What does the lost + found folder do on Mac OS X?

lost + found folder on the hard drive

My "Macintosh HD" hard drive got full again today and I'm using my favorite tool "Daisydisk” walked through the record to see what was taking up all the space. I got my hands on a folder in the main directory called “lost+found” and contained a file called “iNode43817759” with a whopping 5,2 GB.

lost + found folder on the hard drive
Lost+found folder on Mac hard drive is important for storing data related to file system.

Since the whole thing seemed very unfamiliar to me, I did a bit of research to find out what kind of folder this is and what kind of strange file this is.

First of all, here is an explanation of the folder that I found in a forum:

This folder is created by the file system scan if it finds files or folders that are no longer available but are also not correctly marked as “deleted”. So it is assumed that these files/folders were lost in a file system error.
The UNIX tool "filesystem consistency check and interactive repair", fsck for short, is used by the disk service panorama to check the volume (= file system). It can also be done without the FDP via the Port or run at boot.
The purpose of the folder is the same as the mentioned “Recovered Files”. The user should see if there is anything important among the lost files and then restore it. If nothing relevant is included then you can delete the directory. It is also advisable for the user to keep an overview if orphaned data is found again during a later check.

Now that sounds like you could delete the folder and the file it contained, but in a thread in the Apple support forum I found another post that contains this paragraph:

found in http://en.wikipedia.org/wiki/Inode: A file system relies on data structures that contain information about the files, beside the file content. The former is called metadata — data which describes data. Each file is associated with an inode, which is identified by an integer number, often referred to as an i-number or inode number.

Inodes store information about files and folders, such as file ownership, access mode (read, write, execute permissions), and file type. On many types of file system implementations, the maximum number of inodes is fixed at file system creation, limiting the maximum number of files the file system can hold. A typical allocation heuristic for inodes in a file system is one percent of total size.

Too German and in a nutshell

The iNode files are important collection points in Linux systems for file rights, file types and the like. Accordingly, they are not visible to normal users in Mac OS X and should not be deleted.

And if you have only now found the folder under OS X Yosemite and think that this phenomenon is new: Isn't it ... other users have already discovered the folder under OS X Lion. ;-)

 

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